[RFC PATCH v2 04/22] iommu/amd: Report SEV-TIO support

[Alexey Kardashevskiy <aik@amd.com>]

The AMD BIOS'es "SEV-TIO" switch is reported to the OS via IOMMU
Extended Feature 2 register (EFR2), bit 1.

Add helper to parse the bit and report the feature presense.

Signed-off-by: Alexey Kardashevskiy <aik@amd.com>
---
 drivers/iommu/amd/amd_iommu_types.h | 1 +
 include/linux/amd-iommu.h           | 2 ++
 drivers/iommu/amd/init.c            | 9 +++++++++
 3 files changed, 12 insertions(+)

diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index 0bbda60d3cdc..b086fb632990 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -108,6 +108,7 @@
 
 
 /* Extended Feature 2 Bits */
+#define FEATURE_SEVSNPIO_SUP	BIT_ULL(1)
 #define FEATURE_SNPAVICSUP	GENMASK_ULL(7, 5)
 #define FEATURE_SNPAVICSUP_GAM(x) \
 	(FIELD_GET(FEATURE_SNPAVICSUP, x) == 0x1)
diff --git a/include/linux/amd-iommu.h b/include/linux/amd-iommu.h
index 062fbd4c9b77..cb1b94fdb63c 100644
--- a/include/linux/amd-iommu.h
+++ b/include/linux/amd-iommu.h
@@ -32,10 +32,12 @@ struct task_struct;
 struct pci_dev;
 
 extern void amd_iommu_detect(void);
+extern bool amd_iommu_sev_tio_supported(void);
 
 #else /* CONFIG_AMD_IOMMU */
 
 static inline void amd_iommu_detect(void) { }
+static inline bool amd_iommu_sev_tio_supported(void) { return false; }
 
 #endif /* CONFIG_AMD_IOMMU */
 
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index c5cd92edada0..9f2756d3bd73 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -2156,6 +2156,9 @@ static void print_iommu_info(void)
 		if (check_feature(FEATURE_SNP))
 			pr_cont(" SNP");
 
+		if (check_feature2(FEATURE_SEVSNPIO_SUP))
+			pr_cont(" SEV-TIO");
+
 		pr_cont("\n");
 	}
 
@@ -3856,4 +3859,10 @@ int amd_iommu_snp_disable(void)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(amd_iommu_snp_disable);
+
+bool amd_iommu_sev_tio_supported(void)
+{
+	return check_feature2(FEATURE_SEVSNPIO_SUP);
+}
+EXPORT_SYMBOL_GPL(amd_iommu_sev_tio_supported);
 #endif
-- 
2.47.1